Dodge: 1999 2500 Dodge Ram, dodge ram 1999, vacuum leak

Question
I have a 2500 Dodge Ram (1999) and have just replaced the fuel pump.  It still seems to hesitate and want to stall when taking off.  Just recently, my wife was sitting at our sons school with the engine off.  When she started it up and put it into drive, it shut off.  The truck would not start for the next half hour.  It was cranking over but wouldn't start.  The battery is fine.  What is the problem?  Is it the relay?  Is it the ignition module?  Is there any way to find out so that you don't waste money nickel and diming yourself about it?  Please help.  Thank you.

Answer
make sure everything at the distributor is tight,no loose connections,also around the alternator.Check for restricted exhaust system,a catalytic converter will cause this.Put your hand over the exhaust pipe to see if it's restricted.A vacuum leak at the manifold or throttle body can cause it,check all vacuum lines and make sure they are not loose or cracked.